This invention relates to a display device for displaying operating conditions of an electrical machine such as an electrophotographic copying machine. These machines, which transport a medium such as paper, are required to transport the medium at high speed to increase the treatment speed. However, the higher the transporting speed, the greater is the incidence of jamming of the transported medium in the transportation path. When jamming occurs, this electrical machine stops transportation of all of the transported medium behind the jammed one, and at the same time stops all the functions of the electrical machine. In this case, it is necessary for the operator to take out the jammed medium to remove the cause of the fault in order to quickly regain the operation of the electrical machine. Therefore, it is most important for the operator to detect the cause of the fault. To meet this demand, as shown in U.S. Pat. No. 4,176,941, it has been made possible for the operator to detect the faulty part by means of a device displaying a schematic representation of the electrophotographic machine and also displaying on the schematic the location of the jam (in case paper jamming occurs) or other fault.
However, though it is made possible for the operator to detect the faulty part on this displaying device, it is difficult for the unskilled operator (i.e., one who is not a key-operator) to understand how to remedy the fault.
Since the faulty condition continues for many hours unless it is corrected by an experienced operator (i.e., a key-operator) trained in the repair procedure, the prior art display device is inconvenient, since the electrical machine must be easily operated by anyone in the office.